Solve for $k$ : $-9 + k = 3$
Answer: Add $9$ to both sides: $ \begin{eqnarray} \\ -9 + k &=& 3 \\ \\ {+9} && {+9} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-9 + k} &\hphantom{=}& \hphantom{3} \\ k &=& 3 {+ 9} \\ \end{eqnarray} $ Simplify. $ k = 12$